Urbanization typically reduces the extent and quality of riparian areas, via the removal of native vegetation and the development of near-stream areas (Fig 4). These alterations can contribute to multiple instream stressors, including:

Direct modification of stream channels is common in urban systems, and these direct alterations of channel morphology often are the most damaging changes urban streams experience (see the Physical Habitat module, as well as the Physical Habitat section of this module).

Typical channel alterations in urban streams include:

Channelization (i.e., channel straightening)

Channel hardening or armoring (e.g., lining channels and banks with concrete and riprap)

Creation of dams and impoundments

Stream piping and burial

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Removal of riparian vegetation and channel hardening in an urban stream. Courtesy of U.S. EPA.